Question 1

Which is NOT a property of buffers?

Accepted Answer

A) Buffers resist changes in pH when acids or bases are added or when dilution occurs. 
B) Buffers are a mixture of weak acid and conjugate base. 
C) The pH of a buffer is independent of ionic strength. 
D) The pH of a buffer is dependent on temperature. 
E) Buffers are a mixture of weak bases and conjugate acid. 
A) Buffers resist changes in pH when acids or bases are added or when dilution occurs. 
B) Buffers are a mixture of weak acid and conjugate base. 
C) The pH of a buffer is independent of ionic strength. 
D) The pH of a buffer is dependent on temperature. 
E) Buffers are a mixture of weak bases and conjugate acid. C

Question 2

Which of the following statements is NOT true for weak acids?

Accepted Answer

A) Weak acids are partially ionized. 
B) The conjugate base is A− and its strength is weak. 
C)    
D)   
For the conjugate base. 
E) HA + H2O ⇋ A− + H3O+ 
A) Weak acids are partially ionized. 
B) The conjugate base is A− and its strength is weak. 
C)    
D)   
For the conjugate base. 
E) HA + H2O ⇋ A− + H3O+ D

Question 3

The pH of a weak-base solution is calculated using systematic treatment.Which of the following is NOT an equation needed to solve for pOH?

Accepted Answer

A)    
B) F = [BH+] + [B] 
C) [OH−] = [BH+] + [H+] 
D)    
E) Kw = [H+][OH−] 
A)    
B) F = [BH+] + [B] 
C) [OH−] = [BH+] + [H+] 
D)    
E) Kw = [H+][OH−] A

Question 4

One liter of a pH 5.00 propionic acid buffer with a total concentration of 50 mM must be prepared.Calculate the mmols propionic acid and sodium propionate needed to prepare the buffer.Ka = 1.34 x 10-5 for propionic acid.

Accepted Answer

28.6 mmols sodium pr

Question 5

The pH of a weak-acid solution is calculated using systematic treatment.Which of the following is NOT an equation needed to solve for pH?

Accepted Answer

A)    
B) F = [HA] + [A−] 
C) [H+] = [A−] + [OH−] 
D)    
E) Kw = [H+][OH−] 
A)    
B) F = [HA] + [A−] 
C) [H+] = [A−] + [OH−] 
D)    
E) Kw = [H+][OH−]

Question 6

A student calculates the pOH for a 0.01 M triethanolamine solution to be 4.12.To simplify the math she decided to neglect the change in the formal concentration.Was she justified in her decision? Kb = 5.78 × 10−7

Accepted Answer

A) She was justified,as the change in ×,7.59 × 10−5,is less than 1% of the formal concentration. 
B) She was not justified,as the change in ×,9.92 × 10−3,is greater than 1% of the formal concentration. 
C) She was justified,as the change in ×,1.32 × 10−10,is less than 1% of the formal concentration. 
D) She was not justified,as the change in ×,1.00 × 10−2,is greater than 1% of the formal concentration. 
E) She was justified,as the change in ×,5.78 × 10−5,is less than 1% of the formal concentration. 
A) She was justified,as the change in ×,7.59 × 10−5,is less than 1% of the formal concentration. 
B) She was not justified,as the change in ×,9.92 × 10−3,is greater than 1% of the formal concentration. 
C) She was justified,as the change in ×,1.32 × 10−10,is less than 1% of the formal concentration. 
D) She was not justified,as the change in ×,1.00 × 10−2,is greater than 1% of the formal concentration. 
E) She was justified,as the change in ×,5.78 × 10−5,is less than 1% of the formal concentration.

Question 7

Calculate the percent dissociation for a 0.01 M HCN solution,neglecting activity coefficients.Ka = 6.2 × 10−10 for HCN.

Accepted Answer

0.0249% (Neglecting

Question 8

Which of the following statements is NOT true for weak bases?

Accepted Answer

A) Weak bases partially hydrolyze water. 
B) The conjugate acid is BH+ and its strength is strong. 
C)    
D)   
For the conjugate acid. 
E) B + H2O ⇋ BH+ + OH− 
A) Weak bases partially hydrolyze water. 
B) The conjugate acid is BH+ and its strength is strong. 
C)    
D)   
For the conjugate acid. 
E) B + H2O ⇋ BH+ + OH−

Question 9

There are seven common strong acids.Which of the following statements is NOT true for strong acids?

Accepted Answer

A) Dilute solutions are completely ionized. 
B) HNO2 is a strong acid. 
C) For strong acid solutions with a concentration between 10−6 and 10−8 M,the pH is determined using systematic equilibrium. 
D) For strong acid solutions with concentrations F1F1F1S1F1F1F10 10−6 M,the pH is calculated from the concentration of the strong acid. 
E) For strong acid solutions with concentrations F1F1F1S1F1F1F10 10−8 M,the pH is always 7. 
A) Dilute solutions are completely ionized. 
B) HNO2 is a strong acid. 
C) For strong acid solutions with a concentration between 10−6 and 10−8 M,the pH is determined using systematic equilibrium. 
D) For strong acid solutions with concentrations F1F1F1S1F1F1F10 10−6 M,the pH is calculated from the concentration of the strong acid. 
E) For strong acid solutions with concentrations F1F1F1S1F1F1F10 10−8 M,the pH is always 7.

Question 10

Calculate the pH for a 4.3 × 10−8 M HCl solution with an ionic strength of F1F1F1S1F1F1F10 = 0.1.F1F1F1S1F1F1F10H+ = 0.83,F1F1F1S1F1F1F10OH− = 0.76 and F1F1F1S1F1F1F10Cl− = 0.755.

Accepted Answer

pH = 6.59 (When acti

Question 11

The buffer needed for a capillary electrophoresis experiment must have a pH of 10.0.Which weak acid is the best choice for the buffer? Assume F1F1F1S1F1F1F10 = 0.

Accepted Answer

A) ammonium chloride____________________ pKa = 9.24 
B) disodium phosphate____________________ pKa = 12.38 
C) 3-(Cyclohexylamino)propanesulfonic acid pKa = 10.40 
D) sodium dihydrogen borate____________________ pKa = 12.74 
E) cyclohexylaminoethanesulfonic acid____________________pKa = 9.39 
A) ammonium chloride____________________ pKa = 9.24 
B) disodium phosphate____________________ pKa = 12.38 
C) 3-(Cyclohexylamino)propanesulfonic acid pKa = 10.40 
D) sodium dihydrogen borate____________________ pKa = 12.74 
E) cyclohexylaminoethanesulfonic acid____________________pKa = 9.39

Question 12

The rule of thumb for neglecting the change in the formal concentration of a weak acid or a weak base,x,during an equilibrium problem is valid:

Accepted Answer

A) if the change in x is greater than 1% of the formal concentration. 
B) if the change in x is less than 0.1% of the formal concentration. 
C) if the change in x is equal to 0.1% of the formal concentration. 
D) if the change in x is less than 10% of the formal concentration. 
E) if the change in x is less than 1% of the formal concentration. 
A) if the change in x is greater than 1% of the formal concentration. 
B) if the change in x is less than 0.1% of the formal concentration. 
C) if the change in x is equal to 0.1% of the formal concentration. 
D) if the change in x is less than 10% of the formal concentration. 
E) if the change in x is less than 1% of the formal concentration.

Question 13

A buffer is prepared by mixing 200.0 mL of 0.1500 M NaOH with 200.0 mL of 0.200 M CH3CO2H in a 1-L volumetric flask and then diluted to volume with distilled deionized water.Calculate the pH of the buffer.Ka = 1.75 × 10−5

Accepted Answer

A) 5)23 
B) 9)72 
C) 7)00 
D) 8)77 
E) 4)28 
A) 5)23 
B) 9)72 
C) 7)00 
D) 8)77 
E) 4)28

Question 14

There are two types of metal hydroxides,soluble metal hydroxides and insoluble hydroxides,both of which are strong bases.Which of the following statements is NOT true for strong bases?

Accepted Answer

A) Dilute solutions are completely dissociated. 
B) Fe(OH)2 is a strong soluble base. 
C) For strong base solutions with a concentration between 10−6 and 10−8 M,the pOH is determined using systematic equilibrium. 
D) For strong base solutions with concentrations F1F1F1S1F1F1F10 10−6 M,the pOH is calculated from the concentration of the strong base. 
E) For strong base solutions with concentrations F1F1F1S1F1F1F10 10−8 M,the pOH is always 7. 
A) Dilute solutions are completely dissociated. 
B) Fe(OH)2 is a strong soluble base. 
C) For strong base solutions with a concentration between 10−6 and 10−8 M,the pOH is determined using systematic equilibrium. 
D) For strong base solutions with concentrations F1F1F1S1F1F1F10 10−6 M,the pOH is calculated from the concentration of the strong base. 
E) For strong base solutions with concentrations F1F1F1S1F1F1F10 10−8 M,the pOH is always 7.

Question 15

A 0.01 M solution of a weak base has a percent association of 18.32%.Calculate the Kb for the weak base.

Accepted Answer

A) 1)83 × 10−3 
B) 2)43 × 10 −11 
C) 5)46 × 10−12 
D) 4)11 × 10−4 
E) 1)22 × 10−12 
A) 1)83 × 10−3 
B) 2)43 × 10 −11 
C) 5)46 × 10−12 
D) 4)11 × 10−4 
E) 1)22 × 10−12

Question 16

Calculate the percentage dissociation for a 0.010 M hypochlorous acid solution.The Ka for hypochlorous acid is 3.0 x 10−8.

Accepted Answer

A) 0)35% 
B) 0)30% 
C) 0)17% 
D) 0)99% 
E) 0)65% 
A) 0)35% 
B) 0)30% 
C) 0)17% 
D) 0)99% 
E) 0)65%

Question 17

For a 0.0005 M HBr solution,the dissociation of water produces____________________ H3O+ and____________________ OH−.

Accepted Answer

A) 1)00E-07 M;2.00E-11 M 
B) 5)00E-04 M;5.00E-04 M 
C) 2)00E-11 M;2.00E-11 M 
D) 1)00E-07 M;1.00E-07 M 
E) 5)00E-04 M;2.00E-11 M 
A) 1)00E-07 M;2.00E-11 M 
B) 5)00E-04 M;5.00E-04 M 
C) 2)00E-11 M;2.00E-11 M 
D) 1)00E-07 M;1.00E-07 M 
E) 5)00E-04 M;2.00E-11 M

Question 18

Calculate the pH of a 0.2 M ethylamine solution.Kb = 5.0 × 10−4

Accepted Answer

pH = 12.30 (If students report

Question 19

Which of the following is NOT true for weak acids and weak bases?

Accepted Answer

A) Kw = KaF1F1F1S1F1F1F10Kb 
B)    
C)    
D) pKa = −log Ka 
E) pKb = −log Kb 
A) Kw = KaF1F1F1S1F1F1F10Kb 
B)    
C)    
D) pKa = −log Ka 
E) pKb = −log Kb

Question 20

Calculate the pH of 0.01 M HCN (F1F1F1S1F1F1F10 = 0.10)using activity coefficients,neglecting activity coefficients,and the percent difference between the two.Ka = 6.2 x 10−10 for HCN.F1F1F1S1F1F1F10H+ = 0.83,F1F1F1S1F1F1F10OH− = 0.76 and F1F1F1S1F1F1F10CN− = 0.755.

Accepted Answer

pH_activities = 5.20.pH = 5.30.

Exam 10: Monoprotic Acid-Base Equilibria

Which is NOT a property of buffers?

Which of the following statements is NOT true for weak acids?

The pH of a weak-base solution is calculated using systematic treatment.Which of the following is NOT an equation needed to solve for pOH?

One liter of a pH 5.00 propionic acid buffer with a total concentration of 50 mM must be prepared.Calculate the mmols propionic acid and sodium propionate needed to prepare the buffer.Ka = 1.34 x 10-5 for propionic acid.

The pH of a weak-acid solution is calculated using systematic treatment.Which of the following is NOT an equation needed to solve for pH?

A student calculates the pOH for a 0.01 M triethanolamine solution to be 4.12.To simplify the math she decided to neglect the change in the formal concentration.Was she justified in her decision? Kb = 5.78 × 10−7

Calculate the percent dissociation for a 0.01 M HCN solution,neglecting activity coefficients.Ka = 6.2 × 10−10 for HCN.

Which of the following statements is NOT true for weak bases?

There are seven common strong acids.Which of the following statements is NOT true for strong acids?

Calculate the pH for a 4.3 × 10−8 M HCl solution with an ionic strength of  = 0.1.H+ = 0.83,OH− = 0.76 and Cl− = 0.755.

The buffer needed for a capillary electrophoresis experiment must have a pH of 10.0.Which weak acid is the best choice for the buffer? Assume  = 0.

The rule of thumb for neglecting the change in the formal concentration of a weak acid or a weak base,x,during an equilibrium problem is valid:

A buffer is prepared by mixing 200.0 mL of 0.1500 M NaOH with 200.0 mL of 0.200 M CH3CO2H in a 1-L volumetric flask and then diluted to volume with distilled deionized water.Calculate the pH of the buffer.Ka = 1.75 × 10−5

There are two types of metal hydroxides,soluble metal hydroxides and insoluble hydroxides,both of which are strong bases.Which of the following statements is NOT true for strong bases?

A 0.01 M solution of a weak base has a percent association of 18.32%.Calculate the Kb for the weak base.

Calculate the percentage dissociation for a 0.010 M hypochlorous acid solution.The Ka for hypochlorous acid is 3.0 x 10−8.

For a 0.0005 M HBr solution,the dissociation of water produces____________________ H3O+ and____________________ OH−.

Calculate the pH of a 0.2 M ethylamine solution.Kb = 5.0 × 10−4

Which of the following is NOT true for weak acids and weak bases?

Calculate the pH of 0.01 M HCN ( = 0.10)using activity coefficients,neglecting activity coefficients,and the percent difference between the two.Ka = 6.2 x 10−10 for HCN.H+ = 0.83,OH− = 0.76 and CN− = 0.755.

The Analytical Process

Chemical Measurements

Tools of the Trade

Experimental Error

Statistics

Quality Assurance and Calibration Methods

Chemical Equilibrium

Let the Titrations Begin

Activity and the Systematic Treatment of Equilibrium

Polyprotic Acid-Base Equilibria

Acid-Base Titrations

Edta Titrations

Advanced Topics in Equilibrium

Fundamentals of Electrochemistry

Electrodes and Potentiometry

Redox Titrations

Electroanalytical Techniques

Fundamentals of Spectrophotometry

Applications of Spectrophotometry

Spectrophotometers

Atomic Spectroscopy

Mass Spectrometry

Introduction to Analytical Separations

Gas Chromatography

High-Performance Liquid Chromatography

Chromatographic Methods and Capillary Electrophoresis

Gravimetric and Combustion Analysis

Sample Preparation

Filters

One liter of a pH 5.00 propionic acid buffer with a total concentration of 50 mM must be prepared.Calculate the mmols propionic acid and sodium propionate needed to prepare the buffer.K_a = 1.34 x 10^-5 for propionic acid.

A student calculates the pOH for a 0.01 M triethanolamine solution to be 4.12.To simplify the math she decided to neglect the change in the formal concentration.Was she justified in her decision? K_b = 5.78 × 10⁻⁷

Calculate the percent dissociation for a 0.01 M HCN solution,neglecting activity coefficients.K_a = 6.2 × 10⁻¹⁰ for HCN.

Calculate the pH for a 4.3 × 10⁻⁸ M HCl solution with an ionic strength of  = 0.1._H+= 0.83,_OH₋= 0.76 and _Cl₋ = 0.755.

A buffer is prepared by mixing 200.0 mL of 0.1500 M NaOH with 200.0 mL of 0.200 M CH₃CO₂H in a 1-L volumetric flask and then diluted to volume with distilled deionized water.Calculate the pH of the buffer.K_a = 1.75 × 10⁻⁵

A 0.01 M solution of a weak base has a percent association of 18.32%.Calculate the K_b for the weak base.

Calculate the percentage dissociation for a 0.010 M hypochlorous acid solution.The K_a for hypochlorous acid is 3.0 x 10⁻⁸.

For a 0.0005 M HBr solution,the dissociation of water produces H₃O⁺ and OH⁻.

Calculate the pH of a 0.2 M ethylamine solution.K_b = 5.0 × 10⁻⁴

Calculate the pH of 0.01 M HCN ( = 0.10)using activity coefficients,neglecting activity coefficients,and the percent difference between the two.K_a = 6.2 x 10⁻¹⁰ for HCN._H+= 0.83,_OH₋= 0.76 and _CN₋ = 0.755.